In recent years it has been a tendency to increase the weft insertion frequencies and thus the beat-up frequencies in looms having a single phase weft insertion and beat-up. However, a drawback of these higher weaving frequencies is the fact that the warp yarn threads and the weft thread yarn are exposed to larger stress as compared to the respective stress in looms with lower weaving frequencies. Thus, limits to the weaving frequency are set by the strength of the weft and warp yarns. Another limitation factor to be considered is the wear of the yarns that is caused by the higher stress to which these yarns are exposed. The fiber wear in turn results in an increased fly lint and dust production inside the loom and in the air around the loom on the weaving floor.
Investigations regarding the fly lint distribution in the loom show that about 75% of the fiber or thread wear takes place in the area of the rear shed while about 20% take place in the area of the heald frame. In the area of the loom backrest and in the area of the lamellae or drop wires the thread wear results primarily in sizing dust while in the area of the rear shed and of the heald frame the thread wear results primarily in fly lint. The cause for the thread wear or fiber wear is the mutual friction between the warp threads and the forceful opening or separation of weft threads tending to stick to each other when the shed is being opened.
French Patent Publication 1,385,540 (Reiterer et al.) describes a cleaning apparatus for looms having a pneumatic blowing head arranged above the weaving plane. Incidentally, the weaving plane is defined as a plane extending substantially horizontally and tangentially to the beat-up line and to the top of the loom backrest. The blower head is movable back and forth above the weaving plane displaceable across the weaving width. A plurality of downwardly extending blowing nozzles are directed onto the weaving plane. Inside the loom and below the weaving plane there is arranged a suction device with a funnel-shaped suction opening. The funnel forming the suction opening has relatively flat funnel walls with surfaces reaching in the direction of the warp thread run-in in such a way that the funnel covers the area of the warp thread guide and the area of the shed formation. The suction device further has a portion below the funnel which extends substantially vertically.
A funnel-shaped suction device as disclosed in the above mentioned French Patent Publication has the disadvantage that its relatively flat walled suction opening requires an enormously high suction power in order to produce enough suction in the area of the suction opening for the intended dust removal. A high suction power requires a high energy consumption. Experience has shown that even where the suction device cooperates with a simultaneously operating blower head, deposition and sticking of fly lint and other dust components is unavoidable on the surfaces of the suction device that extend relatively flat or approximately parallel to the weaving plane. Thus, it is necessary, to remove these contaminations by additional efforts, for example, by a manual cleaning.
Swiss Patent Publication 584 302 (Muller) discloses a pneumatic cleaning device on a loom, especially a ribbon loom, wherein blower nozzles are arranged below the weaving plane, especially in the area of the shed formation. These blowing nozzles are directed toward the shed formation area. A suction device is arranged above the weaving plane, especially in the area of the shed formation opposite the blower nozzles. In such a cleaning device the blower nozzles are stationary in the loom. Thus, the blower nozzles are not adaptable to the variable conditions in the area of the shed formation. For example, it is not possible without substantial redesign to adapt the blower nozzles to a changed rear shed when a shuttleless or rapier loom is to be reset from two heald frames to maximally twenty-eight heald frames. In such a situation the stationary blower nozzles do not achieve the required cleaning effect with the enlarged number of heald frames. The limitation in the variability of the blower device with regard to its adaptability to various shed formations is thus a substantial drawback.
German Patent Publication DE-OS 1,919,229 (Gleaton et al.) discloses another possibility of removing fly lint and the like from a loom. A large number of blow nozzles which are movable back and forth above the weaving plane in a loom emit air jets of such a strength that any fly lint depositions are blown away or these jets make sure that depositions do not occur in the first place. The air nozzles emit flow speeds in the range of about 300 to 6000 m/min. since the blowing nozzle arrangement does not cooperate with a suction device, a substantial problem is generated because the lint flies into the air of the weaving hall so that avoiding the problem of a proper lint removal in accordance with environmental requirements is not assured.
German Patent Publication 1,679,571 (Black, Jr.) discloses a pneumatical cleaning device for the removal of fly lint depositions. The device is mounted on a bridge that is movable back and forth and can be positioned above the loom. The blower head of this known cleaning apparatus comprises at least one downwardly directed blowing nozzle reaching toward the loom. The fly lint that is caught by the airstream from the blowing nozzle is blown into the interior of the loom where it is intercepted by a stationary arranged floor suction device. Such a blowing nozzle is conventionally spaced relatively far away from the floor suction nozzle of the loom, so that a controlled interception of the fly lint whirled up by the blowing air is not assured, regardless how powerful the floor suction nozzles might be.